There are various types of connecting structures for medical use for connecting medical components such as tubes. A connecting structure for medical use of the type disclosed in Patent Document 1 (Unexamined Utility Model Publication No. S59-87840) is described below with reference to FIGS. 22 and 23.
The connecting structure for medical use includes a male assembly 1 and a female connector 2.
The male assembly 1 includes a male connector 10 and a threadedly engageable cylinder 20 rotatably attached to the male connector 10. The male connector 10 includes a male luer portion 11 having a tapered outer periphery. The threadedly engageable cylinder 20 includes a threadedly engageable portion 21 disposed outside of the male luer portion 11 of the male connector 10 in a radial direction. A female screw 21a is formed in an inner periphery of the threadedly engageable portion 21.
The female connector 2 includes a female luer portion 2a having a tapered inner periphery. Engageable protrusions 2c threadedly engageable with the female screw 21a is formed in an outer periphery of a distal end portion of the female luer portion 2a. 
As shown in FIG. 22, when the threadedly engageable cylinder 20 is turned in a tightening direction with the female screw 21a of the threadedly engageable cylinder 20 and the engageable protrusions 2c of the female connector 2 threadedly engaged, the male luer portion 11 and the female luer portion 2a are joined together. When the threadedly engageable cylinder 20 is turned further in the tightening direction, the male luer portion 11 and the female luer portion 2a are tightly joined together with a pressing force, providing sufficient sealing properties.
When the threadedly engageable cylinder 20 is in a tightened state, a surface 21x on a deeper side of a screw thread of the female screw 21a is strongly abutted against the engageable protrusions 2c, thereby drawing the female luer portion 2a toward the male luer portion 11. By friction between the surface 21x on the deeper side of the screw thread of the female screw 21a and the engageable protrusions 2c, the threadedly engageable cylinder 20 keeps the female luer portion 2a in the drawn state, thereby keeping the male luer portion 11 and the female luer portion 2a in the joined state.